Safety syringe assembly

ABSTRACT

A hypodermic safety syringe assembly ( 10 ) includes a cylindrical barrel ( 12 ) having a front end defining a first aperature ( 14 ) and a rear end defining a second aperature ( 16 ), a closure member ( 32 ) shaped to engage the barrel ( 12 ) at or adjacent the front end thereof to seal the first aperature ( 14 ), and a piston assembly ( 18 ) reciprocally movable within the barrel ( 12 ) and includes a retractor ( 20 ) terminating in a piston formation ( 24 ) engageable with the closure member ( 32 ) to disengage the closure member from the front end of the barrel so that a hypodermic needle ( 40 ) attached thereto can be withdrawn into the barrel ( 12 ) after use, wherein the closure member ( 32 ) includes a barrel engaging formation ( 44,48 ) releasably engageable within a closure member engaging formation ( 64 ) at the front end of the barrel ( 12 ), and a piston coupling formation ( 50,54 ) for engaging a closure member coupling formation ( 68,69 ) on the piston ( 24 ), with inter-engagement of the piston and closure member coupling formations ( 50,54;68,69 ) being arranged to facilitate disengagement of the barrel engaging and closure member engaging formations ( 64; 44,48 ) from one another and to allow withdrawal of the piston assembly ( 20,24 ), closure member ( 32 ) and hypodermic needle ( 40 ) into the barrel ( 12 ).

BACKGROUND OF THE INVENTION

This invention relates to a hypodermic safety syringe assembly.

The needles of used hypodermic syringes pose an increasing threat of thetransmissibility of potentially lethal infections such as HIV⁺ andhepatitis B viruses, not only to persons administering the injection,but also to persons who are charged with handling such equipmentimmediately after use, to others who are exposed to the possibility ofaccidental, post-injection contact in environments in which hypodermicprocedures are routinely administered, and to still others who mightcome into contact with used syringes which have been inadequatelydisposed of.

Various safety hypodermic syringes have been designed which attempt tominimise these risks. These include various forms of needle containmentand needle disposal units which respectively seek to encapsulate a usedneedle or allow such used needle to be destroyed by incineration or thelike. In order to be effective, needle destroying devices have to beavailable in situ at all locations where such procedures are undertaken.The effectiveness of needle destroying devices is further reduced by thefact that the sharp end of the used needle may typically be exposed foran appreciable period of time before it is destroyed.

Another arrangement which is available comprises a cylindrical sleevewhich fits around the barrel of a syringe, and which can be extendedforward over the needle attached to the syringe after use. When thesleeve is fully extended, locking formations on the sleeve engagecomplemental locking formations formed on or adjacent the end of thesyringe barrel so that the sleeve cannot be retracted.

Drawbacks of protective sleeve arrangements include the fact that in anumber of such devices the shield has an open end, which is large enoughto allow a user's finger to enter and to contact the needle. A directlyconcomitant disadvantage is the fact that in order to obviate thisdanger, the needle used has to be substantially shorter than the lengthof the syringe barrel and shield. The extended and locked syringe/sleeveassembly is relatively long and bulky, and uses a substantial additionalmass of plastic material compared with the syringe alone. Arrangementsof this type are also relatively complicated to manufacture, frequentlyinvolving a complete re-engineering of the syringe in order for it toco-operate in secure locking engagement with the sleeve. Examples areprovided by the disclosures in U.S. Pat. Nos. 5,053,018 and 5,304,149,both of which teach a hypodermic syringe and needle assembly on which ismounted a shield which is movable between a retracted position in whichthe needle point is exposed and an extended position in which the needlepoint is covered.

User resistance has been encountered to the added bulk and overalldiameter of the assembly contributed by the sleeve, which isparticularly disadvantageous when the needle point needs to be acutelytangential to the surface of the skin of the patient. The fact that thecontents and the graduations on the syringe must be viewed through thematerial of the shield has also proved inconvenient and can lead toerrors in use.

An alternative arrangement where the syringe is substantiallyre-engineered typically proposes a device having a barrel, sheath andpiston, the piston being provided with a liquid passagewayinterconnectable with the barrel. The injection of fluid is accomplishedby moving the barrel relative to the sheath (as opposed to the morefamiliar approach of moving the piston relative to the barrel, inconventional hypodermic syringe assemblies). An example of this approachis provided by South African Patent 93/5302, which teaches the automaticand non-discretionary single use safe rendition of a needle.

Three disadvantages of this approach have manifested themselves inpractice. The first is the fact that the procedure represents asignificant departure from the operation of a conventional syringe.Nursing staff have shown resistance to the required adjustment from whatis a comfortable and familiar routine. A further disadvantage is thefact that this approach requires a large number of component parts,which adds significantly to the cost of both the moulds and mouldoperations required and of the materials used. A final disadvantage isthe impression left with the practitioner that the precise point whenthe device is rendered needle-safe is no longer a matter of professionalchoice, but is rather a matter of when the manufacturer has prescribedthat it is advisable or necessary.

The highest incidence of the HIV⁺ and hepatitis viruses generally occurin poor, third world countries which can ill afford devices reliant onsignificant re-engineering, which do not take into account the highlevel of the capital invested world-wide in manufacturing facilities forand stocks of conventional hypodermic syringes and needles.

It is an object of the invention to provide an alternative safetysyringe assembly which allows for an administering procedure which doesnot depart significantly from that of a conventional syringe, and whichdoes not utilise an additional outer sheath or shield.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided ahypodermic safety syringe assembly including a cylindrical barrel havinga front end defining a first aperture and a rear end defining a secondaperture, a closure member shaped to engage the barrel at or adjacentthe front end thereof to seal the first aperture, and a piston assemblyreciprocally movable within the barrel and including a retractorterminating in a piston formation engageable with the closure member todisengage the closure member from the front end of the barrel so that ahypodermic needle attached thereto can be withdrawn into the barrelafter use, wherein the closure member includes a barrel engagingformation releasably engageable within a closure member engagingformation at the front end of the barrel, and a piston couplingformation for engaging a closure member coupling formation on thepiston, with inter-engagement of the piston and closure member couplingformations being arranged to facilitate disengagement of the barrelengaging and closure member engaging formations from one another and toallow withdrawal of the piston assembly, closure member and hypodermicneedle into the barrel.

The closure member preferably includes an inner skirt portion connectedto an outer skirt portion by a hinge, with a displacement groove locatedbetween the inner and outer skirt portions.

The barrel engaging formation preferably includes a lip extending fromthe outer skirt portion, and the closure member engaging formationpreferably includes a lip receiving recess adjacent the front end of thebarrel.

The piston coupling formation preferably includes at least one firstprojection and a corresponding projection receiving recess locatedradially outwardly of the first projection, and the closure membercoupling formation preferably includes a second projection and acorresponding recess located radially inwardly of the second projection,with the second projection being arranged to displace the firstprojection inwardly about the hinge during inter-engagement of thepiston coupling formation and closure member coupling formation so as tourge the outer skirt formation, from which the first projection depends,inwardly so as to disengage the lip from the lip receiving recess.

The first projection is preferably a first annular lobe formation andthe second projection is preferably a second annular lobe formation.

The assembly preferably includes detaining means for detaining the usedneedle in a locked safe position within the barrel.

An embodiment of the invention is described in detail in the followingpassages of the specification which refer to the accompanying drawings.The drawings, however, are merely illustrative of how the inventionmight be put into effect, so that the specific form and arrangement ofthe features shown is not to be understood as limiting on the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partly cross-sectioned side view of a safety syringeassembly according to the invention;

FIG. 2A shows an underplan view of a closure member forming part of thesafety syringe assembly of FIG. 1;

FIG. 2B shows a cross-sectional side view along the line 2B-2B of FIG.2A;

FIGS. 3A to 3C show cross-sectional detailed side views of the manner inwhich the closure member engages the front end of the barrel duringassembly of the safety syringe assembly of the invention;

FIGS. 3D to 3H show, stepwise, the procedure involved in the pistonformation engaging with and retracting the closure member into thebarrel of the safety syringe assembly;

FIG. 4 shows a partly cross-sectioned side detailed view of the pistonformation and closure member in a retracted engaged position; and

FIG. 5 shows a partly cross-sectioned side view of the safety syringe inthe retracted engaged position.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to FIG. 1, safety syringe assembly 10 of the inventioncomprises a barrel 12 having a front opening 14 and a rear opening 16. Apiston assembly 18 is arranged to travel reciprocally within the barrel12 and includes an elongate retractor 20 having a cruciform profileterminating in a rear finger disc 22. A piston formation 24 extends fromthe front end of the retractor, and includes front and rear piston discs26 and 28 and an O-ring 30 located within an intervening annular recess31. The front piston disc 26 is coupled to a closure member 32 formedwith a central spigot formation 34 extending from a skirt 36. A needlehub 38 fits over the needle spigot 34 in a snug friction fit, and aneedle 40 extends from the needle hub 38.

Referring now to FIGS. 2A and 2B, the skirt 36 of the closure member 32includes a rigid inner skirt portion 42 and an outer peripheralrelatively flexible skirt portion 44 which is arranged to flex about anarrowed neck portion defining a radially hooped hinge 46. The outerperipheral flexible skirt portion 44 terminates in a barrel-engaging lip48. A series of piston-engaging lobes 50 extend axially inwardly andradially outwardly from the back of the flexible skirt portion 44. Thelobes 50 are arranged in an annulus, with a total of 24 lobes beingdefined by evenly spaced gaps 52 therebetween which are designed toreduce hoop stress and facilitate inward flexure of the flexible skirtportion 44. A piston-receiving recess 54 is defined between the freeends of the lobes 50 and the lip 48 of the flexible skirt. There is adisplacement groove 74 between the inner skirt portion 42 and outerskirt portion 44.

Referring now to FIGS. 3A to 3C, the syringe barrel 12 terminates in aninwardly extending flange 56, and defines a round cylindrical innersurface 58 which extends for almost the entire length thereof. A ramp 60extends between the cylindrical surface 58 and a reduced diameter land62, and a lip-locating recess or groove 64 is located between the land62 and the flange 56. The closure member 32 is fitted to the syringebarrel by inserting it through the rear opening 16 thereof. As theclosure member 32 travels down the barrel, the flexible skirt portion 44is marginally flexed inwardly as the lip 48 contacts the inner surface58 of the barrel. As the lip 48 rides up the ramp 60 and onto thereduced diameter land 62, the outer flexible skirt portion 44 flexesinwardly in the direction of arrow 65 about the hinge 46, as is clearfrom FIG. 3B. Further forward movement of the closure member 32 causesthe barrel-engaging lip 48 to locate firmly within the lip receivingrecess 64 at the front end of the barrel, with the outer skirt portion44 being in a partly inwardly flexed position.

When the closure member 32 is in the forward engaged position of FIG.3C, a pushing force in the direction of arrow 67A translates into anoutwardly pivoting movement of the outer flexible skirt portion 44 inthe direction of arrow 67B. This has the effect of expanding the outerdiameter of the skirt portion and jamming the lip 48 of the skirt evenmore tightly within the detent or recess 64.

After administration of the injection, the piston formation 24 is movedforwards within the barrel 12 to the position indicated in FIG. 3D. Thefront piston disc 26 is formed with an outer closure member-engaginglobe 68 and an adjacent lobe-receiving recess 69 for receiving the lobe50 of the closure member 32. As the piston formation 24 advances to theFIG. 3E position, an outer peripheral rib formation 70 bears firmlyagainst the ramp 60. As the outer diameter of the rib 70 is greater thanthe progressively decreasing inner diameter of the ramp 60, this resultsin the relatively rigid front piston disc 26 beginning to outwardlydeform the syringe barrel 12, as is indicated by bulge 72. The barrel 12is typically formed from a softer grade of polypropylene than the pistonformation to facilitate the outward deformation of the barrel walls.

In the FIG. 3E position, the geometry of the arrangement is such thatthe outermost points of the first piston-engaging lobes 50 and thesecond annular closure member-engaging lobe 68 are tangential. Furtheradvancement of the piston formation induces a complex combination offorces which ultimately result in the first set of lobes 50 rotatinginwardly about the hinge 46 in the direction of the arrow in thedisplacement groove 74. The displacement groove 74 permits inwardrotation of the first set of lobes 50.

In the engaged position of FIG. 3G, the piston formation 24 and theclosure member 32 are fully inter-engaged, with the second annular lobe68 nesting within the recess 54 defined between the lobe 50 and theouter lip 48, and the first set of lobes 50 nesting within the annularrecess 69 defined within the front piston disc 26. In this position,further outward deformation of the barrel occurs at 76. The extent ofdeformation can clearly be seen in FIG. 3F, where the degree of overlapbetween the front piston disc 26 and the non-deformed barrel wall 12 isshown at 78. The radially inward movement of the lobe 50 results in thelip 48 being disengaged from the recess 64 and a clearance gap 80 beingdefined. As is clear from FIG. 3H, the now coupled piston assembly 18and closure member 32 can be retracted by virtue of the simultaneousinter-engagement of the lobes 50 and 68 and the disengagement of the lip48 from the recess 64.

The piston assembly 18, closure member 32 and needle hub assemblyincluding the used needle 40 and the needle hub 38 are subsequentlyretracted fully to the FIGS. 4 and 5 position in which the used needlepoint is locked safely within the syringe barrel, with the narrowdiameter opening 14 constituting a finger barrier. It can clearly beseen how the inner surface of the barrel wall 12 has been profiled witha piston formation and closure member-detaining land 82 being definedbetween a front rib or detent 84 and a rear rib or detent 86 of reduceddiameter, with the rear rib 86 being sufficiently prominent to preventboth the rear and front piston discs 28 and 26 respectively from beingretracted out of the barrel. The lip 48 of the outer skirt portion islocated just behind the rib 84 which detains it in the fully retractedposition, and prevents subsequent forward movement of the inter-engagedpiston formation and closure member which carries the needle hub andused needle 40. A frangible connection 88 is provided between the rearpiston disc 28 and the retractor 20. The frangible connection 88 hasbeen designed so that it has both tensile and compressive strength in anaxial direction, but is weak in the shear vector which allows theretractor to be broken off in the manner illustrated. Both the retractorand the syringe barrel safely housing the used needle can now bedisposed of.

1. A hypodermic safety syringe assembly including a cylindrical barrelhaving a front end defining a first aperture and a rear end defining asecond aperture, a closure member shaped to engage the barrel at oradjacent the front end thereof to seal the first aperture, and a pistonassembly reciprocally movable within the barrel and including aretractor terminating in a piston formation engageable with the closuremember to disengage the closure member from the front end of the barrelso that a hypodermic needle attached thereto can be withdrawn into thebarrel after use, wherein the closure member includes a barrel engagingformation releasably engageable within a closure member engagingformation at the front end of the barrel, and a piston couplingformation for engaging a closure member coupling formation on thepiston, with inter-engagement of the piston and closure member couplingformations being arranged to facilitate disengagement of the barrelengaging and closure member engaging formations from one another and toallow withdrawal of the piston assembly, closure member and hypodermicneedle into the barrel.
 2. The assembly of claim 1 wherein the closuremember includes an inner skirt portion connected to an outer skirtportion by a hinge, with a displacement groove located between the innerand outer skirt portions.
 3. The assembly of claim 2 wherein the barrelengaging formation includes a lip extending from the outer skirtportion, and the closure member engaging formation includes a lipreceiving recess adjacent the front end of the barrel.
 4. The assemblyof claim 3 wherein the piston coupling formation includes at least onefirst projection and a corresponding projection receiving recess locatedradially outwardly of the first projection, and the closure membercoupling formation includes a second projection and a correspondingrecess located radially inwardly of the second projection, with thesecond projection being arranged to displace the first projectioninwardly about the hinge during inter-engagement of the piston couplingformation and closure member coupling formation so as to urge the outerskirt formation, from which the first projection depends, inwardly so asto disengage the lip from the lip receiving recess.
 5. The assembly ofclaim 4 wherein the first projection is a first annular lobe formationand the second projection is a second annular lobe formation.
 6. Theassembly of any one of the above claims including detaining means fordetaining the used needle in a locked safe position within the barrel.